The improvement of metal containing anodes has been of particular interest in the development of electrochemical cells such as batteries, for example. Lithium (Li) metal, as one example, may be particularly useful as the anode of electrochemical cells because of its relatively light weight and high energy density, as compared to other types of anode materials (e.g., carbon, metals). Automobiles to portable electronic devices (e.g., laptops, cellular phones) may include batteries which comprise lithium anodes. Historically, lithium anodes in electrochemical cells experience decreased performance with power cycling, the decreased performance resulting from self discharge. As a result, lithium anodes have not been adopted for commercial rechargeable batteries.
Published literature has shown that the surface of lithium metal may be covered by various Li-salts, including (but not limited to) carbonate, oxide, hydroxide. The surface layer on the lithium metal, which may be non-homogenous in thickness and composition, which may lead to uneven current distribution across the lithium surface, during plating and/or stripping. As a result of this inhomogeneous current distribution, the surface layer under the Li-salts may become non-uniform or roughen with successive cycles charge/discharge. In extreme cases, non-uniformity of the lithium surface may result in mossy lithium (i.e., lithium not connected to the current collector) or dendrites. Either case may result in reduced battery performance, although the latter is also a potential source of battery self-discharge and even thermal runaway.
Numerous solutions have been proposed to prevent the formation of mossy and/or dendritic deposits on the lithium surface, including the addition of polymers and other protective layers and formation of dense layers on the lithium surface by chemical treatment, either in-situ or ex-situ. Despite various approaches to improve metal anodes, a need remains for processes and compositions to improve the homogeneity of metal anode surfaces and thus, increase performance of electrochemical cells.